Prusa Mini+ and the Revo Micro

Installing the Revo Micro on the Prusa Mini+

I finally had a chance to try out the Revo Micro hotend from E3D over Memorial Day weekend and it didn’t go as smoothly as I had hoped. Hopefully others can learn from my mistakes and save themselves a little bit of time. TLDR; Use Edition 2 with the stock fan for the Revo Micro with the Prusa Mini.

Revo Micro

The E3D Revo RapidChange system was all the buzz late 2021 and quickly sold out everywhere early 2022. It offers a lot of great benefits (with some added cost). The biggest feature of course, is being able to quick change a nozzle all while having no leakage between the hotend and the heat break.

As cool as it looked, I held off and waited to try the new hotend system. After all, my printers were working just fine…. Were. Fast forward to late spring 2022 and I had a failed thermistor on my Mini+. Finally! I had a good reason to dip my toes into the Revo ecosystem! I ordered a fully loaded 24v Revo Micro from Printed Solid and patiently waited for it to arrive in the mail.

Revo Micro Installation on the Prusa Mini+

Unboxing the Revo Micro was straight forward. However, there was zero documentation in the box, and if I didn’t lift up and look under the box insert I would have easily missed the extension cables. Since there was no installation instructions I used the Google and eventually landed on the instructions for the ‘Revo Micro – Prusa Mini upgrade guide (Edition 1)’.

There was an ‘Edition 2’ set of instructions, but the only difference I could see was Edition 1 used the fan that came with the Revo Micro, and Edition 2 used the existing stock fan.

I decided to install Edition 1, since using the old stock fan didn’t seem ideal. Afterall, a fan that came with the Revo Micro would surely be better, right?

While printing the Edition 1 mount on another Prusa Mini, I disassembled my hotend and got it prepared for the installation.

Installation was easy enough and I was up and printing with PETG in no time. The Revo Micro was tiny and cute and I was pleased with the upgrade. I was sold and ready to order another one for my other Prusa Mini! but I’m glad I waited…

Heat Creep Issues

After a few successful PETG prints with the Revo Micro w/Edition 1, I switched over to some PLA filament. Right away on the first layer, the filament started to click and grind in the extruder and nothing was coming out of the hotend. I unloaded the PLA filament and the extruder had ground down a notch in the filament.

I reloaded the filament and the filament purged out of the hotend like normal so there was no clog. I began printing again and the same thing happened again. Surely something was wrong.. was it my esteps? did I need to PID tune? what was it? So I began to Google…

Edition 1 vs Edition 2

After Googling and reading forum post after forum post with people experiencing the same issue, I came to the conclusion that the problem was the small fan that comes with the Revo Micro and the Edition 1 mount. The fan itself wasn’t to blame, it was a combination of factors..

It turns out the Prusa Mini firmware runs the hotend fan at 38% speed and there is no way to adjust that speed without modifying the firmware. Another option would be to rewire the fan wires to the board so the ground is attached to a different pin and that would run the fan at 100% at all times. Both seemed like viable solutions but a little overkill and kludgey.

Since the Edition 2 version of the hotend mount uses the larger stock fan, it is able to cool the heatsink more effectively. I decided to print an Edition 2 mount and replace the tiny fan with the larger stock fan. The stock fan also has a tachometer wire, so it doesn’t fail when doing fan self tests.

Once I had the Edition 2 mount installed with the stock fan, I was able to do some new tests with PLA. Everything worked as expected and I no longer experienced any heat creep, clogging or extruder clicking.

Summary

In conclusion, I think E3D is doing the average user a disservice by still publishing the Edition 1 version of instructions. If you are going to install the Revo Micro on your Prusa Mini+ you should ditch the little fan that comes with the Revo Micro hotend and use the stock fan with the Edition 2 mount or you’ll experience nothing but grief!

Happy Printing!